LONDON, March 2 (Reuters) - President Vladimir Putin said on Thursday Russia had been hit by a "terrorist attack" in the southern Bryansk region bordering Ukraine, and vowed to crush what he said was a Ukrainian sabotage group that had fired at civilians.
Ukraine accused Russia of staging a false "provocation", but also appeared to imply some form of operation had indeed been carried out by Russian anti-government partisans.
Amid reports of shelling and sporadic sabotage, Russia's border regions have become increasingly volatile since Moscow invaded Ukraine a year ago in what it called a "special military operation".
Putin, in a televised address, accused the group of opening fire on civilians in a car, including children. Bryansk Governor Alexander Bogomaz said the attack had killed two people and wounded an 11-year-old boy.
"They won't achieve anything. We will crush them," said Putin, saying the group was made up of the kind of people who wanted to rob Russia of its history and language.
The FSB security service said in an initial statement that the army and FSB were trying to liquidate "an armed group of Ukrainian nationalists" who had crossed the border.
In a later update, the FSB said the situation was under the control of law enforcement agencies. It said a large number of explosive devices had been found and demining was taking place. It did not mention earlier reports by state news agencies that hostages had been taken.
In two videos circulating online, armed men calling themselves the "Russian Volunteer Corps" said they had crossed the border to fight what they referred to as "the bloody Putinite and Kremlin regime."
Describing themselves as Russian "liberators", the armed men called on Russians to take up arms and rise up against the authorities. They said they did not open fire on civilians.
Reuters could not immediately verify the videos' authenticity.
Kremlin spokesman Dmitry Peskov told reporters that law enforcement agencies would determine who was responsible and Putin was being briefed by security chiefs on the situation.
KIEV ACCUSES MOSCOW OF 'PROVOCATION'
Ukrainian presidential adviser Mykhailo Podolyak wrote on Twitter: "The story about (a) Ukrainian sabotage group in RF (Russian Federation) is a classic deliberate provocation."
He said Russia "wants to scare its people to justify the attack on another country & the growing poverty after the year of war."
A spokesman for Ukrainian military intelligence suggested the makeup of the sabotage group was a sign of internal strife inside Russia.
"These are people who with weapons in their hands are fighting the Putin regime and those who support it... Maybe Russians will begin to wake up, realise something and take some concrete steps," Andriy Yusov told Ukrainian outlet Hromadske.
British military intelligence said on Wednesday that Russia was launching drone attacks on Ukraine from the Bryansk region, which lies to the north of Ukraine and is closer to its capital Kyiv than other launch sites.
Russia has accused Ukrainian saboteurs of infiltrating Bryansk before. In December, the FSB said a four-person Ukrainian "sabotage group" had been "liquidated" while trying to enter the region.
Putin told the FSB this week that it needed to step up its guard against espionage and what he called terrorist threats emanating from Ukraine and the West.
"Your task is to put a barrier in the way of sabotage groups, to stop attempts to illegally transport weapons and ammunition into Russia," he said in a speech on Tuesday.
